- Electronic and Photonic Devices and Systems fPeranti dan Sistem Elektronik dan FotonikJ

UNIVERSITI

SAINS

MALAYSIA

KSCP Semester Examination Academic Session ^{2007 12008}

June 2008

7/I{E

32313

- Electronic and Photonic Devices and Systems fPeranti dan Sistem Elektronik dan FotonikJ

Duration:

3 hours

[Masa :

³

jamJ

Please ensure that this examination paper contains

FIVE

printed pages before you begin the examination.

[Sila

pastilran bahawa kertas peperilesaan

ini

mengandungi

LIMA

muka surat yang bercetak sebelum anda memulakan peperiksaan ini.J

Instruction:

Answer

all FIVE

questions. Students are allowed

to

answer

all

questions in Bahasa Malaysia or in English.

[@:

Jau,ab semua

LIMA soalan. Pelajar

dibenarkan menjanab semua soalan sama ada dalam Bahasa Malaysia atau Bahasa Inggeris.J

...2t-

1. (a)

(c)

lzY,E ³²³¹

-2-

Sketchthe

I-V

characteristics

of

an idealZener diode and

showits

accurate equivalent

circuit.

^State

the condition for

a proper

working of the

Zenet diode

in

^a circuit.

[Latrarlrnn ciri-ciri I-V suatu dtod Zener unggul dan tuniukkan litar

setaranya

yang tepat.

^{Nyatakan kzadaan}

bagi diod

Zener untuk berfungsi dengan baik dalam suatu

litar.J

(20l100)

The circuit in Figure 1

^shows

a simple voltage

^regulator

using a

Zener

diode.

Describe how the

circuit

operates.

[Litar dalam Rajah I

menuniuk]ran

suatu pengatur voltan

mudah

menggunakan diod Zener. Perihalknn bagaimana litar

tersebut beroperasi.J

Figure

| [Rajah IJ

(40/100)

With

reference

to

an n-channel JFET, show how the device is driven

into

a saturation

and'offl

^states.

fDengan merujukkepada JFET terusan-n, tuniukkan bagaimana

peranti ini

dipandu kepada keadaan-keadaan tepu

dan 'of'.J

(40/100) (b)

...3/-

2. (a)

(a)

(a)

^ [2Y.E323)

-J-

With a simple circuit,

^show

how a

JFET

is

employed

in an optical fiber communication system which processes signals received from

^a

photodiode. Then, describe

in brief

how the signal transmission takes place and why JFET is suitable for this application.

[Dengan

^suatu

litar

mudah, tunjuklmn bagaimana suatu

JFET

digunaknn dalam sistem komunilmsi serabut

optik yang

memproses

isyarat

diterima

dari fotodtod. Seterusnya, jelasknn dengan ringkas

bagaimana

penghantaran isyarat berlalat dan mengapa JFET sesuai

dalam penggunaan ini-J

(s0/100)

Describe how the operational

of LASCR

devices is used

in AND/

OR logic

circuit

and

in

a relay system.

[Perihalknn

^dengan

jelas

bagaimana operasi

peranti

LASCR digunakan dalam

litar

logik AND/OR dan dalom

sistem

^'relay'.J

(50/r00)

Discuss

the

process

of photon

generation

in a LED with the help of

an

energy band diagram and show the I-V output

characteristics

and

the generated power characteristics.

[Bincanglran proses penghasilan

foton dari suatu LED

^{dengan bantuan}

gambarajah

jalur

tenaga dan tunjukknn

ciri

output

I-V

dan

ciri

kuasa

yang

dihasilkan.J

(s0l100)

An LED

has a carrier recombination

lifetime of t :

_{38 ns} and

a

radiative

lifetime

of

rr:60

^ns

in

^{an active region.}

If

^generated

light

has l" = 0.87 pm at a

drive

current

of 40 mA,

estimate the internal quantum

efficiency

and the internal optical power of the

LED.

fSuatu LED

mempunyai masa hayat gabungan

pembtwa t : 38 ns

^dan

masa hayat

radiatif q : 60 ns dalam kanasan ahif' Jika

cahaya yang

dihasilknn

mempunyai

). :

0.87 pm

pada

arus

pandu 40

mA, anggarknn kecelrapan lwantum dalaman dan

luasa

optik dalaman

LED'J

(s0/100)

Describe the process

of

laser generation

in

a p-n

junction of

semiconductor and show the role

of

optical cavity

for

^a high efficiency laser.

fPerihatlrnn ^proses penghasilan laser

dari

simpang

p-n semilanduhor

dan tunjuklran peranan rongga optik

bagi

kecelmpan

tinggi

laser tersebut.J

(sol100) (b)

3.

(b)

4.

(b)

lzr<83231

-4-

A

laser

of

GaAs has a device

efficiency of

10%.

If

the voltage used

is

2.5

V,

determine the extemal quantum efficiency

of

the device. Then, estimate

the differential external

^quantum

efficiency at a high current

injection.

Describe the effect on the device external quantum efficiency if

the injection current is reduced but

still

higher than threshold current.

[Suatu laser

dari

bahan GaAs mempunyai lcecekapan

peranti

sebesar 10o%.

Jilra

voltan

yang

digunakan adalah

2.5

V,

kira

kecekapan

htantum

luaran

peranti ini.

Seterusnya, anggarkan kecekapan

lanntum luaran

diferensial

pada arus

cucuknn

tinggi.

Jelaskan kesan kepada keceknpan htantum luaran peranti

jika

arus cucuksn dikurangkan tetapi masih lebih besar

dari

arus arnbang.J

(

E

^{bagi GaAs}

:

^{1.43 eV)}

[( Et

-for ^GaAs

:

1.43 eV)J

(s0/r00)

(a)

For ^a p-n photodiode,

[Bagi

^suatu fotodiod ^p-n,

J

(i)

describe the operational principle.

[per ihallmn pr insiP ^{oPer as i.}

J

(ii) determine the cut-off wavelength for the light absorption of

^a

semiconductor

with

energy gaP Ee ^.

[tentukan paniang

gelombang

penggal bagi penyerapan

cahaya untuk

semilanduhor

denganiurang tenaga

Et.J

(iiD

sketch

atypical

output characteristic.

flalcnrknn

ciri

outPut tiPilml.J

(s0/100)

State the Pockels effect and the Kerr effect of

electro-optic materials.

fNyatalcan kesan Pockels dan kesan

Kerr

bagi bahan

elelaro'optikJ

Show how a

transverse

modulator can be built to

^modulate the phase of optical wave that pass through electro-optic materials.

[Tunjuklran bagoimana suatu modulator melintang dapat dibina bagi

memodulasikan

fasa gelombang optik yang melalui

^bahan eleWro-optikJ

5.

(i)

(ii)

(b)

...51-

IZKE

³²³¹

-5-

(iii)

^{State the}

principle of

a directional optical coupler, sketch the output

for power

exchange

that

occurs

in the identical coupler (without

phase

mismatched) and sketch a diagram for the related

3-dB coupler.

[Nyatakan prinsip pengganding optik berarah , lakarkan

^output

bagi tukarganti

kuasa

yang berlalat dalam pengganding

seiras

(tanpa

taksepadanan

fasa) dan laknrknn gambaraiah

bagi pengganding 3 -dB berkaitan.J

(s0/100)

-oooOooo-